Amanda Seyfried & Justin Long: Are They a Summer Item?

Amanda Seyfried, 27, has been spotted numerous times this summer with iSteve actor Justin Long, 35, most recently Thursday night at Cecconi's restaurant in West Hollywood, Calif.

"They looked like they were on a dinner date," an onlooker told PEOPLE. "She was in a festive mood."

According to the source, Seyfried – dressed in a black tank and black, wide-brimmed hat – and Long sipped on white wine. "They were both smiling and looked so happy," the onlooker said. "She looked like she was very into him."

Another diner also spotted them.

"They seemed happy and you can tell they are newly dating," says the observer. "They are engaged in the conversation and seem intrigued in what each other has to say. They are very cute."

Seyfried and Long were also seen together at the July 30 Cinema Society premiere of Lovelace in New York. The two were seen looking "cozy" at the movie's after-party on the Refinery Rooftop lounge, a source tells PEOPLE.